Actinic radiation curable compositions and their use

ABSTRACT

Actinic radiation curable compositions comprising at least one actinic radiation curable, cationically polymerizable compound and at least one cationic photoinitiator, may be stabilized by the use of a stabilizer which is a complex of a Lewis acid (other than a fluorine-containing boron compound) and a Lewis base.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is the National Phase of International ApplicationPCT/GB03/02410 filed Jun. 4, 2003 which designated the U.S. and waspublished in English and which claims priority to G.B. Pat. App. No.0212977.3, filed Jun. 6, 2002. The noted applications are incorporatedherein by reference.

The present invention relates to actinic radiation curable compositionsand their use.

Curable compositions containing epoxy resins are very well known. Manyare heat curable. For example, U.S. Pat. Nos. 4,341,819, 5,688,878,5,780,560, 5,932,288 and 6,316,049 describe heat curable compositionscontaining an epoxy together with a crosslinking agent of themethylenedisalicylic acid type. The cure catalyst in U.S. Pat. No.6,316,049 may be a BF₃:amine complex in which the amine is primary,secondary, or tertiary and has a boiling point of about 106° C. orbelow.

Actinic radiation curable liquid resins or resin mixtures are veryversatile. For example, they can be used as coating compositions,adhesives or photoresists. They may also be used for the manufacture ofthree-dimensional objects using stereolithography. In this technique thedesired shaped article is built up from a liquid, radiation-curablecomposition with the aid of a recurring, alternating sequence of twosteps (a) and (b); in step (a), a layer of the liquid, radiation-curablecomposition, one boundary of which is the surface of the composition, iscured with the aid of appropriate radiation, generally radiationproduced by a preferably computer-controlled laser source, within asurface region which corresponds to the desired cross-sectional area ofthe shaped article to be formed, at the height of this layer, and instep (b) the cured layer is covered with a new layer of the liquid,radiation-curable composition, and the sequence of steps (a) and (b) isrepeated until a so-called green model of the desired shape is finished.This green model is, in general, not yet fully cured and must therefore,normally, be subjected to post-curing.

Much work has been put into developing suitable actinicradiation-curable compositions for the uses mentioned above. For exampleU.S. Pat. No. 5,476,748 describes a novel photosensitive compositioncomprising an epoxy resin and a cationic photoinitiator therefortogether with a cycloaliphatic or aromatic diacrylate and a radicalphotoinitiator therefor, and an OH-terminated polyether, polyester orpolyurethane.

A major problem with actinic radiation curable compositions is that theytend to have low storage stability. Such compositions generally containa component whose purpose is to initiate curing in the presence ofradiation, and this component may be unstable under storage conditions.In such a case, small concentrations of certain species, typicallyphotoacids, can cause the composition to discolour and to gel even ifkept under cool dark conditions. Thus, EP 153904A, EP 35969A, EP 44272A,EP 54509A, EP 164314A and U.S. Pat. No. 3,708,296 describe onium saltswhich may be used as initiators for radiation curable epoxycompositions. These salts are highly effective initiators. However, theyhave the disadvantage that they can break down on storage to producesmall quantities of the corresponding acids which can initiate thecuring of the epoxy compound present in the composition. This in turnleads to an increase in viscosity of the composition, and can causegellation or even actual hardening of the composition in a relativelyshort period of time.

U.S. Pat. No. 5,665,792 discloses stabilisers for photohardenable epoxycompositions, which have limited solubility in the composition and adensity which is different from that of the composition, and which aresalts of a Group IA or Group IIA metal ion and a weak acid, the weakacid having a pKa in water of greater than 3.0.

There is a need for stabilizers which will increase the shelf life ofactinic radiation curable epoxy compositions without adversely affectingthe properties of the compositions, particularly now as new means ofdispensing actinic radiation curable compositions are becomingavailable, for example, piezo ink jet printing.

It is known that certain complexes of boron-containing compounds withamines can be used in epoxy compositions as curing agents. U.S. Pat. No.6,242,513 discloses epoxy-containing compositions and at least one Lewisacid catalyst. Amongst the materials listed as suitable catalysts areborane-amine complexes and amino complexes of boron halides. Thecatalyst is preferably present in the composition in an amount of from0.4% to about 0.8% by weight. U.S. Pat. No. 6,191,681 describes anelectrically conductive composite material including an epoxy togetherwith a Lewis acid catalyst, such as a boron trichloride- or borontrifluoride-amine complex. The complex is used in an amount of about 4%by weight based on epoxy. In all these cases, the boron-amine complex isused as a catalyst, its objective being to initiate curing of the epoxy.Other documents which describe curable compositions containingboron-containing complexes include U.S. Pat. No. 5,124,234, U.S. Pat.No. 5,694,852, U.S. Pat. No. 4,632,891, WO 88/00096, JP 030255185 and JP560053129. In all of these documents, the complex is used as a curingagent, sometimes but not always in conjunction with a cationicphotoinitiator.

It has now been found that certain complexes can act as stabilizers forepoxy compounds and other cationically polymerisable compounds inactinic radiation-curable compositions also containing a cationicphotoinitiator, for example an onium compound, provided that the amountof complex is limited appropriately. The fact that they can act asstabilisers, i.e. that they prevent premature curing of the cationicallycurable compound, is most surprising in view of their well-known use ascuring initiators for epoxies.

The invention therefore provides an actinic radiation curablecomposition comprising:

-   (A) at least one actinic radiation curable, cationically    polymerisable compound;-   (B) at least one cationic photoinitiator for component (A); and-   (C) at least one stabiliser which is a complex of a Lewis acid and a    Lewis base, provided that the Lewis acid is not a    fluorine-containing boron compound; component (C) being present in    the composition in an amount of from 0.001 to 0.3 wt % and the    relative amounts of Component (B) and Component (C) being such that    the composition is stabilised relative to the corresponding    composition in which Component (C) is not present.

Any actinic radiation curable, cationically polymerisable compound maybe present in component (A) of a composition according to the invention.Epoxy compounds are preferred, and such epoxy compounds may have analiphatic, aromatic, cycloaliphatic, araliphatic or heterocyclicstructure; they may comprise epoxy groups as side groups, or thosegroups form part of an alicyclic or heterocyclic ring system. Preferredepoxies are those having an epoxy functionality of greater than or equalto 2. Preferably the composition contains at least 50 wt % of epoxycompound.

There may be mentioned as examples of epoxy resins of the type:

I) Polyglycidyl and poly(β-methylglycidyl) esters obtainable by thereaction of a compound having at least two carboxy groups in themolecule and epichlorohydrin or glycerol dichlorohydrin orβ-methyl-epichlorohydrin. The reaction is advantageously effected in thepresence of bases.

Aliphatic polycarboxylic acids can be used as compounds having at leasttwo carboxy groups in the molecule. Examples of those polycarboxylicacids are glutaric acid, adipic acid, pimelic acid, suberic acid,azelaic acid, sebacic acid or dimerised linoleic acid.

It is, however, also possible to use cycloaliphatic poly carboxylicacids, such as, for example, tetrahydrophthalic acid,4-methyltetrahydrophthalic acid, hexahydrophthalic acid or4-methylhexahydrophthalic acid.

It is also possible to use aromatic polycarboxylic acids, such as, forexample, phthalic acid, isophthalic acid, trimellitic acid orpyromellitic acid.

It is likewise possible to use carboxy-terminated adducts, for exampleof trimellitic acid and polyols, such as, for example, glycerol or2,2-bis(4-hydroxycyclohexyl)propane.

II) Polyglycidyl or poly(P-methylglycidyl) ethers obtainable by thereaction of a compound having at least two free alcoholic hydroxy groupsand/or phenolic hydroxy groups and a suitably substitutedepichlorohydrin under alkaline conditions, or in the presence of anacidic catalyst with subsequent alkali treatment. Ethers of that typeare derived, for example, from acyclic alcohols, such as ethyleneglycol, diethylene glycol and higher poly(oxyethylene) glycols,propane-1,2-diol, or poly (oxypropylene) glycols, propane-1,3-diol,butane-1,4-diol, poly(oxytetramethylene) glycols, pentane-1,5-diol,hexane 1,6-diol, hexane-2,4,6-triol, glycerol, 1,1,1-trimethylolpropane,bistrimethylolpropane, pentaerythritol, sorbitol, and also frompolyepichlorohydrins.

They are, however, also derived, for example, from cycloaliphaticalcohols, such as 1,3- or 1,4-dihydroxycyclohexane,bis(4-hydroxycyclohexyl)methane, 2,2-bis(4-hydroxycyclohexyl)propane or1,1-bis(hydroxymethyl)cyclohex-3-ene, or they possess aromatic nuclei,such as N,N-bis(2-hydroxyethyl)aniline orp,p-bis(2-hydroxyethylamino)diphenylmethane.

The epoxy compounds may also be derived from mononuclear phenols, suchas, for example, from resorcinol or hydroquinone, or they are based onpolynuclear phenols, such as, for example, bis-(4-hydroxyphenyl)methane(bisphenol F), 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), or oncondensation products, obtained under acidic conditions, of phenols orcresols with formaldehyde, such as phenol novolaks and cresol novolaks.

(III) Poly(N-glycidyl) compounds are, for example, obtainable bydehydrochlorination of the reaction products of epichlorohydrin withamines that comprise at least two amine hydrogen atoms. Those aminesare, for example, n-butylamine, aniline, toluidine, m-xylylene diamine,bis(4-aminophenyl)methane or bis(4-methy-laminophenyl)methane.

The poly(N-glycidyl) compounds also include, however, N,N-diglycidylderivatives of cycloalkyleneureas, such as ethyleneurea or1,3-propyleneurea, and N,N′-diglycidyl derivatives of hydantoins, suchas of 5,5-dimethylhydantoin.

IV) Examples of poly(S-glycidyl) compounds are di-S glycidyl derivativeswhich are derived from dithiols, such as, for example,ethane-1,2-dithiol or bis(4-mercaptomethylphenyl) ether.

V) Examples of epoxy compounds in which the epoxy groups form part of analicyclic or heterocyclic ring system are bis(2,3-epoxycyclopentyl)ether, 2,3-epoxycyclopentyl glycidyl ether,1,2-bis(2,3-epoxycyclopentyloxy)ethane, bis(4-hydroxycyclohexyl)methanediglycidyl ether, 2,2-bis(4-hydroxycyclohexyl)propane diglycidyl ether,3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane,3,4-epoxy-6-methyl-cyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate,di-(3,4-epoxycyclohexylmethyl) hexanedioate,di-(3,4-epoxy-6-methyl-cyclohexylmethylenebis(3,4-epoxycyclohexanecarboxylate),ethanediol di-(3,4-epoxycyclohexylmethyl) ether, vinylcyclohexenedioxide, dicyclopentadiene diepoxide or2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-1,3-dioxane.

It is, however, also possible to use epoxy resins in which the 1,2-epoxygroups are bonded to different hetero atoms or functional groups. Thosecompounds include, for example, the N,N,O-triglycidyl derivative of4-aminophenol, the glycidyl ether glycidyl ester of salicylic acid,N-glycidyl-N′ (2-glycidyloxypropyl)-5,5-dimethylhydantoin or2-glycidyloxy-1,3-bis(5,5-dimethyl-1-glycidylhydantoin-3-yl)propane.

Especially preferred are compositions containing a cycloaliphaticdiepoxide, for example bis(4-hydroxycyclohexyl)methane diglycidyl ether,2,2-bis(4-hydroxycyclohexyl)propane diglycidyl ether,3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate,3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate,di-(3,4-epoxycyclohexylmethyl)hexanedioate,di-(3,4-epoxy-6-methyl-cyclohexylmethyl)hexanedioate,ethylenebis(3,4-epoxycyclohexanecarboxylate), ethanedioldi-(3,4-epoxy-cyclohexylmethyl) ether or2-(3,4-epoxycyclohexyl)-5,5,3-dioxane. The monomer purity of anycycloaliphatic diepoxide is preferably 90% or higher.

Curable commercial epoxy products that can be used herein include:Uvacure 1500, Uvacure 1501, Uvacure 1502, Uvacure 1530, Uvacure 1531,Uvacure 1532, Uvacure 1533, Uvacure 1534, Uvacure 1561, Uvacure 1562,all commercial products of UCB Radcure Corp., Smyrna, Ga.; UVR-6105,UVR-6100, UVR-6110, UVR-6128, UVR-6200, UVR-6216 of Union Carbide Corp.,Danbury, Conn.; the Araldite GY series that is Bisphenol A epoxy liquidresins, the Araldite CT and GT series that is Bisphenol A epoxy solidresins, the Araldite GY and PY series that is Bisphenol F epoxy liquids,the cycloaliphatic epoxides Araldite CY 179 and PY 284, the Araldite DYand RD reactive diluents series, the Araldite ECN series of epoxy cresolnovolacs, the Araldite EPN series of epoxy phenol novolacs, allcommercial products of Ciba Specialty Chemicals Corp., the Heloxy 48,Heloxy 44, Heloxy 84 and the other Heloxy product line, the EPON productline, all of Shell Corp., the DER series of flexible aliphatic andBisphenol A liquid or solid epoxy resins, the DEN series of epoxynovolac resins, all commercial products of Dow Corp., Celoxide 2021,Celoxide 2021P, Celoxide 2081, Celoxide 2083, Celoxide 2085, Celoxide2000, Celoxide 3000, Glycidole, AOEX-24, Cyclomer A200, Cyclomer M-100,Epolead GT-300, Epolead GT-302, Epolead GT-400, Epolead 401, Epolead403, (Daicel Chemical Industries Co., Ltd.), Epicoat 828, Epicoat 812,Epicoat 872, Epicoat CT 508, (Yuka Shell Co., Ltd.), KRM-2100, KRM-2110,KRM-2199, KRM-2400, KRM-2410, KRM-2408, KRM-2490, KRM-2200, KRM-2720,KRM-2750 (Asahi Denka Kogyo Co., Ltd.).

In addition, liquid pre-reacted adducts of such epoxy resins withhardeners are suitable for use as component (A).

Cationically curable cyclic compounds other than epoxies which may beused in the compositions of the invention include oxetanes, oxolanes,cyclic acetals, anhydrides, cyclic lactones, thiiranes, and thiotanes.Typical oxetane compounds include trimethylene oxide,3,3-dimethyloxetane and 3,3-dichloromethyloxetane,3-ethyl-3-phenoxymethyloxetane, and bis(3-ethyl-3-methyloxy)butane.Typical oxolane compounds include tetrahydrofuran and2,3-dimethyl-tetrahydrofuran. Typical cyclic acetal compounds includetrioxane, 1,3-dioxalane and 1,3,6-trioxan cycloctane. Typical cycliclactone compounds include β-propiolactone and ε-caprolactone. Typicalanhydrides include phthalic anhydride and terephthalic anhydride andhydroxy-containing derivatives thereof. Typical thiirane compoundsinclude ethylene sulphide, 1,2-propylene sulphide andthioepichlorohydrin. Typical thiotane compounds include 1,3-propylenesulphide and 3,3-dimethylthiothane.

Vinyl ethers that can be used as a cationically polymerisable compoundin the compositions of the invention include ethyl vinylether, n-propylvinylether, isopropyl vinylether, n-butyl vinylether, isobutylvinylether, octadecyl vinylether, cyclohexyl vinylether, butanedioldivinylether, cyclohexanedimethanol divinylether, diethyleneglycoldivinylether, triethyleneglycol divinylether, tert-butyl vinylether,tert-amyl vinylether, ethylhexyl vinylether, dodecyl vinylether,ethyleneglycol divinylether, ethyleneglycolbutyl vinylether, hexanedioldivinylether, triethyleneglycol methylvinylether, tetraethyleneglycoldivinylether, trimethylolpropane trivinylether, aminopropyl vinylether,diethylaminoethyl vinylether, ethylene glycol divinyl ether,polyalkylene glycol divinyl ether, alkyl vinyl ether and3,4-dihydropyran-2-methyl 3,4-dihydropyran-2-carboxylate. Commercialvinyl ethers include the Pluriol-E200 divinyl ether (PEG200-DVE),poly-THF290 divinylether (PTHF290-DVE) and polyethyleneglycol-520 methylvinylether (MPEG500-VE) all of BASF Corp.

Hydroxy-functionalised mono(poly)vinylethers include polyalkyleneglycolmonovinylethers, polyalkylene alcohol-terminated polyvinylethers,butanediol monovinylether, cyclohexanedimethanol monovinylether,ethyleneglycol monovinylether, hexanediol monovinylether,diethyleneglycol monovinylether.

Another class of vinyl ethers that are suitable for inclusion in thecompositions according to the invention are all those included in U.S.Pat. No. 5,506,087, which is incorporated herein by reference. Morepreferred are aromatic or alicyclic vinyl ethers. As an example,commercial vinylethers include Vectomer 4010, Vectomer 5015, Vectomer4020, Vectomer 21010 and Vectomer 2020 of Allied Signal Corp.,Morristown, N.J. Most preferred are Vectomer 4010 and Vectomer 5015.

Other cationically polymerisable compounds include spiro ortho estersthat are prepared by reacting epoxy compounds with lactone; and otherethylenically unsaturated compounds, such as vinylcyclohexane,N-vinyl-2-pyrrolidone and its various derivatives, isobutylene andpolybutadiene, and derivatives of the above compounds.

A mixture of two or more different cationically polymerisable compoundsmay be present in the composition of the invention, depending upon theintended use.

Component (B) is preferably an onium salt with an anion of weaknucleophilicity. Examples are halonium salts, iodosyl salts orsulphonium salts, for example those described in EP 153904A,sulphoxonium salts, for example those described in EP 35969A, EP 44272A,EP 54509A and EP 164314A, and diazonium salts, for example thosedescribed in U.S. Pat. No. 3,708,296. An overview of further known oniumsalt initiators is offered by “UV-Curing, Science and Technology”,(Editor: S. P. Pappas, Technology Marketing Corp., 642 Westover Road,Stamford, Conn., USA) or “Chemistry & Technology of UV & EB Formulationsfor Coatings, Inks & Paints”, Vol. 3 (edited by P. K. T. Oldring). Allof these are incorporated herein by reference.

Preferred compositions comprise, as a cationic photoinitiator, acompound of the formula (I), (II) or (III)

in which each of R₁, R₂, R₃, R₄, R₅, R₆, and R₇ independently of oneanother are C₆-C₁₈aryl which is unsubstituted or substituted byappropriate radicals, and

-   A⁻ is CF₃SO₃ ⁻ or, preferably, an anion of the formula [LQ_(m)]⁻,    where-   L is boron, phosphorus, arsenic or antimony,-   Q is a halogen atom, or some of the radicals Q in an anion LQ_(m) ⁻    may also be hydroxyl groups, and-   m is an integer corresponding to the valency of L enlarged by 1.

Examples of C₆-C₁₈aryl in this context are optionally substitutedphenyl, naphthyl, anthryl and phenanthryl. Suitable optionalsubstituents include alkyl, preferably C₁-C₆alkyl, such as methyl,ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl orthe various pentyl or hexyl isomers, alkoxy, preferably C₁-C₆alkoxy,such as methoxy, ethoxy, propoxy, butoxy, pentoxy or hexoxy, alkylthio,preferably C₁-C₆alkylthio, such as methylthio, ethylthio, propylthio,butylthio, pentylthio or hexylthio, halogen, such as fluorine, chlorine,bromine or iodine, amino groups, cyano groups, nitro groups or arylthio,such as phenylthio. Examples of preferred halogen atoms Q are chlorineand, in particular, fluorine. Preferred anions LQ_(m) are BF₄ ⁻, PF₆ ⁻,AsF₆ ⁻, SbF₆ ⁻ and SbF₅(OH)⁻.

Particularly preferred compositions are those comprising as a cationicphotoinitiator a compound of the formula (III), in which R₅, R₆ and R₇are aryl, aryl being in particular phenyl and/or biphenyl. Commerciallyavailable photoinitiators of this type include the bis-sulphoniumantimony hexafluoro compounds UVI 6974 and UVI 6976.

Component (C) comprises at least one stabiliser which is a complex(sometimes referred to as a coordination compound) of a Lewis acid and aLewis base. A Lewis acid is a substance which can accept an electronpair from a base. A Lewis base is a substance which can donate anelectron pair. The donated electron pair is then shared between acid andbase (see for example Organic Chemistry, John McMurry, Fifth edition, p.57-61; McGraw-Hill Encyclopedia of Science and Technology, Vol 1, p.50-51). The Lewis acid may for example be BX₃, AlX₃, FeX₃, FeX₂, ZnX₂,TiX₃ or TiX₄ where each X independently represents a C(1-6)alkyl orC(1-6)alkoxy group or a hydrogen, chlorine, bromine, iodine or fluorineatom, provided that when the Lewis acid is BX₃ no X represents afluorine atom. Boron trifluoride has been found to be unsuitable for usein the present invention, being ineffective as a stabilizer, insteadacting to cure the composition. Preferably each X is the same. Where Xis an alkyl group, it is preferably an ethyl group. Where X is a halogenatom, it is preferably a bromine, iodine or, especially, chlorine atom.Preferably the Lewis acid is BX₃, especially BH₃ or BCl₃, or an iron IIIhalide, especially FeCl₃ The Lewis base may for example be ammonia,phosphine, an amine or a phosphine. Preferred amines and phosphinesinclude amines and phosphines of the general formulaZ(R₈)₃  (IV)in which Z is nitrogen or phosphorus, and each R₈ independentlyrepresents a hydrogen atom (provided that not more than two R₈ groupsrepresent hydrogen); an alkyl group having from 1 to 20, preferably from1 to 8, for example from 1 to 4, carbon atoms, optionally substituted byone or more phenyl groups (in which the phenyl group may be optionallysubstituted by one or more C(1-12) alkyl groups and/or halogen atoms) orC(5-7)cycloalkyl groups; a phenyl group optionally substituted by one ormore C(1-12)alkyl groups and/or halogen atoms; or a C(5-7)cycloalkylgroup; or two R₈'s together represent an alkylene group having from 4 to6 carbon atoms one or more of which may be replaced by an oxygen or asulphur atom; and in which each alkyl, cycloalkyl or phenyl grouppresent in the compound of the formula IV may be optionally substitutedby one or more, preferably one or two, groups —Z(R₈)₂.

For example, each R₈ may independently represent a C(1-12)alkyl group ora phenyl group.

Preferably the complex is an amine complex.

Such complexes may be made by known methods and many are availablecommercially. Particular examples of suitable complexes include thefollowing: borane ammoniac complex; borane triethylamine complex; boranetributylphosphine complex; borane trimethylamine complex; boranetriphenylphosphine complex; borane tributylamine complex; boraneN,N-diethylamine complex; borane N,N-diisopropylethylamine complex;borane dimethylamine complex; borane N-ethyl-N-isopropyl anilinecomplex; borane 4-methylmorpholine complex; borane 4-ethylmorpholinecomplex; bis-(triethylborane) 1,6-diaminohexane complex; trichloroboraneN,N-dimethyloctylamine complex; trichloroborane triethylamine complex;trichloroborane pyridine complex; trichloroborane benzylamine complex;irontrichloride triethylamine complex; irontrichloride pyridine complex;and irontrichloride N,N-dimethyloctylamine.

Typically the complex contains one equivalent of a Lewis acid perequivalent of Lewis base, for example one equivalent of a compound offormula BX₃ per equivalent of amine or phosphine.

Component (C) of the composition according to the invention is presentin an amount of from 0.001 to 0.3 wt %, preferably from 0.001 to 0.1 wt%. The optimal amount of component (C) present in any particularcomposition will depend upon the amount of cationic photoinitiatorpresent in the composition, as well as on the identity of the particularcomplex and the particular photoinitiator used. In general, the higherthe amount of cationic photoinitiator present, the higher the amount ofcomponent (C) required to give effective stabilisation. The quantity ofcomponent (C) will however be as low as possible as excessive amounts ofcomponent (C), far from stabilising the composition, can lead to gellingor even curing of the composition.

The compositions of the present invention may also contain furthercomponents depending upon the intended use and desired properties of thecompositions. For example, in addition to the cationically polymerisablecompound, the compositions according to the present invention alsopreferably comprise a free radically curable component. This componentpreferably comprises at least one solid or liquid poly(meth)acrylate,for example, di-, tri-, tetra- or pentafunctional monomeric oroligomeric aliphatic, cycloaliphatic or aromatic acrylates ormethacrylates. Such compounds preferably have a molecular weight of from200 to 500.

Examples of suitable aliphatic poly(meth)acrylates having more than twounsaturated bonds in their molecules are the triacrylates andtrimethacrylates of hexane-2,4,6-triol, glycerol or1,1,1-trimethylolpropane, ethoxylated or propoxylated glycerol or1,1,1-trimethylolpropane, and the hydroxyl-containing tri(meth)acrylateswhich are obtained by reacting triepoxide compounds, for example thetriglycidyl ethers of said triols, with (meth)acrylic acid. It is alsopossible to use, for example, pentaerythritol tetraacrylate,bistrimethylolpropane tetraacrylate, pentaerythritolmonohydroxytriacrylate or -methacrylate, or dipentaerythritolmonohydroxypentaacrylate or -methacrylate.

It is additionally possible, for example, to use polyfunctional urethaneacrylates or urethane methacrylates. These urethane (meth)acrylates areknown to the person skilled in the art and can be prepared in a knownmanner by, for example, reacting a hydroxyl-terminated polyurethane withacrylic acid or methacrylic acid, or by reacting anisocyanate-terminated prepolymer with hydroxyalkyl (meth)acrylates togive the urethane (meth)acrylate.

Examples of suitable aromatic tri(meth)acrylates are the reactionproducts of triglycidyl ethers of trihydric phenols and phenol or cresolnovolaks containing three hydroxyl groups, with (meth)acrylic acid.

The (meth)acrylates used herein are known compounds and some arecommercially available, for example from the SARTOMER Company underproduct designations such as SR®295, SR®350, SR®351, SR®367, SR®399,SR®444, SR®454 or SR®9041.

Preferred compositions are those in which the free radically curablecomponent contains a tri(meth)acrylate or a penta(meth)acrylate.

Suitable examples of di(meth)acrylates are the di(meth)acrylates ofcycloaliphatic or aromatic diols such as 1,4-dihydroxymethylcyclohexane,2,2-bis(4-hydroxy-cyclohexyl)propane, bis(4-hydroxycyclohexyl)methane,hydroquinone, 4,4′-dihydroxybi-phenyl., Bisphenol A, Bisphenol F,bisphenol S, ethoxylated or propoxylated Bisphenol A, ethoxylated orpropoxylated Bisphenol F or ethoxylated or propoxylated bisphenol S.Di(meth)acrylates of this kind are known and some are commerciallyavailable.

Other di(meth)acrylates which can be employed are compounds of theformulae (V), (VI), (VII) or (VIII)

in which

-   R₉ is a hydrogen atom or methyl,-   Y is a direct bond, C₁-C₆alkylene, —S—, —O—, —SO—, —SO₂— or —CO—,-   R₁₀ is a C₁-C₈alkyl group, a phenyl group which is unsubstituted or    substituted by one or more C₁-C₄alkyl groups, hydroxyl groups or    halogen atoms, or is a radical of the formula —CH₂—OR₁₁ in which-   R₁₁ is a C₁-C₈alkyl group or phenyl group, and-   A is an alkylene group or a group of the formula

Further examples of possible di(meth)acrylates are compounds of theformulae (IX), (X), (XI) and (XII)

These compounds of the formulae (V) to (XII) are known and some arecommercially available. Their preparation is also described in EP-A-0646 580.

Examples of commercially available products of these polyfunctionalmonomers are KAYARAD R-526, HDDA, NPGDA, TPGDA, MANDA, R-551, R-712,R-604, R-684, PET-30, GPO-303, TMPTA, THE-330, DPHA-2H, DPHA-2C,DPHA-21, D-310, D-330, DPCA-20, DPCA-30, DPCA-60, DPCA-120, DN-0075,DN-2475, T-1420, T-2020, T-2040, TPA-320, TPA-330, RP-1040, R-011,R-300, R-205 (Nippon Kayaku Co., Ltd.), Aronix M-210, M-220, M-233,M-240, M-215, M-305, M-309, M-310, M-315, M-325, M-400, M-6200, M-6400(Toagosei Chemical Industry Co, Ltd.), Light acrylate BP-4EA, BP-4PA,BP-2EA, BP-2PA, DCP-A (Kyoeisha Chemical Industry Co., Ltd.), NewFrontier BPE-4, TEICA, BR-42M, GX-8345 (Daichi Kogyo Seiyaku Co., Ltd.),ASF-400 (Nippon Steel Chemical Co.), Ripoxy SP-1506, SP-1507, SP-1509,VR-77, SP-4010, SP-4060 (Showa Highpolymer Co., Ltd.), NK Ester A-BPE-4(Shin-Nakamura Chemical Industry Co., Ltd.), SA-1002 (MitsubishiChemical Co., Ltd.), Viscoat-195, Viscoat-230, Viscoat-260, Viscoat-310,Viscoat-214HP, Viscoat-295, Viscoat-300, Viscoat-360, Viscoat-GPT,Viscoat-400, Viscoat-700, Viscoat-540, Viscoat-3000, Viscoat-3700 (OsakaOrganic Chemical Industry Co., Ltd.).

If the composition according to the present invention also comprises afree radically curable component it should also contain at least onefree radical initiator. It is possible to employ all types ofphotoinitiators which form free radicals given the appropriateirradiation. Typical representatives of free-radical photoinitiators arebenzoins, such as benzoin, benzoin ethers, such as benzoin methyl ether,benzoin ethyl ether and benzoin isopropyl ether, benzoin phenyl etherand benzoin acetate, acetophenones, such as acetophenone,2,2-dimethoxy-acetophenone and 1,1-dichloroacetophenone, benzil, benzilketals, such as benzil dimethylketal and benzil diethyl ketal,anthraquinones, such as 2-methylanthraquinone, 2-ethylanthraquinone,2-tert-butylanthraquinone, 1-chloroanthraquinone and2-amylanthraquinone, and also triphenylphosphine, benzoylphosphineoxides, for example 2,4,6-trimethylbenzoyl-diphenylphosphine oxide(Luzirin® TPO), bisacylphosphine oxides, benzophenones, such asbenzophenone and 4,4′-bis(N,N′-dimethylamino)benzophenone, thioxanthonesand xanthones, acridine derivatives, phenazine derivatives, quinoxalinederivatives or 1-phenyl-1,2-propanedione 2-O-benzoyl oxime,1-aminophenyl ketones or 1-hydroxy phenyl ketones, such as1-hydroxy-cyclohexyl phenyl ketone, phenyl 1-hydroxyisopropyl ketone and4-isopropylphenyl 1-hydroxyisopropyl ketone, all of which constituteknown compounds. A particularly preferred free radical initiator isIrgacure 184, available from Ciba Speciality Chemicals, which is phenyl1-hydroxycyclohexyl ketone.

Preferably a composition according to the invention comprises from 20 to60 wt % of an cationically polymerisable compound; from 0.1 to 10 wt %of cationic initiator; from 5 to 40 wt % of a radically curablecomponent; from 0.1 to 10% of a radical initiator; and from 0.001 to 0.3wt % of the stabiliser which is a complex of a Lewis acid with a Lewisbase.

The compositions according to the invention may also advantageouslycontain hydroxy compounds, for example as described in U.S. Pat. No.6,379,866, U.S. Pat. No. 5,629,133 and U.S. Pat. No. 5,972,563, forexample hydroxy terminated polyethers, such as polytetrahydrofuran diolsand polyols having a molecular weight of about 250 to about 4000, orsiloxane/polyethylene oxide copolymers.

The present invention is useful for the stabilisation of compositionssuch as those described in U.S. Pat. No. 5,476,748, the contents ofwhich are incorporated herein by reference. Accordingly, in a preferredembodiment of the invention, there is provided a composition accordingto the invention comprising

a) from 40 to 80% by weight of at least one liquid epoxy resin having anepoxy functionality of equal to or greater than 2,

b) from 0.1 to 10% by weight of at least one cationic photoinitiator forcomponent a),

c) from 5 to 40% by weight of at least one liquid diacrylate,

d) from 0 to 15% by weight of at least one liquid poly(meth-)acrylatehaving a (meth-)acrylate functionality of greater than 2, the proportionof component d) preferably constituting a maximum of 50% by weight ofthe total (meth-)acrylate content,

e) from 0.1 to 10% by weight of at least one radical photoinitiator forcomponent c) and, where appropriate, d),

f) from 5 to 40% by weight of at least one OH-terminated polyether,polyester or polyurethane, and

g) at least one stabiliser which is a complex of a Lewis acid and aLewis base, the Lewis acid being other than a fluorine-containing boroncompound; component (g) being present in the composition in an amount offrom 0.001 to 0.3 wt %, and the relative amounts of Component (b) andComponent (g) being such that the composition is stabilised relative tothe corresponding composition in which Component (g) is not present.

The compositions according to the invention can further includecustomary additives for epoxy compositions, such as colouring agents,such as pigments and dyes, antifoaming agents, leveling agents,thickening agents, flame retardants, antioxidants and fillers such assilica, alumina, glass powder, ceramic powder and metal powder.

The novel compositions of the present invention can be prepared in aknown manner by, for example, premixing individual components and thenmixing these premixes, or by mixing all of the components usingcustomary devices, such as stirred vessels, in the absence of light and,if desired, at slightly elevated temperature. The physical form of thecomposition will depend upon the intended application, and may forexample be a powder, a paste, or a liquid.

The novel compositions can be polymerized by irradiation with actinicradiation, for example by means of electron beams, X-rays, UV or VISlight, preferably with radiation in the wavelength range of 280-650 nm.Particularly suitable are laser beams of HeCd, argon or nitrogen, metalvapour lasers, and NdYAG lasers and their frequency doubled or trebledcounterparts.

The invention additionally relates to a method of producing a curedproduct, which comprises treating a composition according to theinvention with actinic radiation. For example, it is possible in thiscontext to use the novel compositions as adhesives, for example in DVDmanufacture, as coating compositions, as photoresists, for example assolder resists, for rapid prototyping, for example by stereolithographyor by ink jet printing, or for inkjet printing for producing visual ornon-visual markings on any substrates. The present invention isparticularly useful in the field of compositions for use instereolithography. The requirements for compositions for use in thisfield are challenging. Liquid compositions for stereolithography usuallyhave a low viscosity, but because the compositions generally contain aninitiator which generates a strong acid, maintaining this low viscosityon storage is difficult. Where the stereolithography composition is apaste, control of viscosity is also very important and premature curingcan be a major problem. The present invention is also particularlyuseful in the field of inkjet printing. Here, jetting of the compositionis often carried out at elevated temperature, and premature gelling orthickening of the printing composition can be a particular problem,leading to blockage of the printing jets. It is an advantage of thepresent invention that stabilisation is obtained not only at roomtemperature or below, but also at elevated temperatures, for examplethose used during inkjet printing, typically around 65° C.

When the novel compositions according to the invention are employed ascoating compositions, the resulting coatings on wood, paper, metal,ceramic, glass, or other surfaces are clear and hard. The coatingthickness may vary greatly and can for instance be from 0.01 mm to about1 mm. Specific coating applications include the coating of opticalfibres, and the production of marine coatings. Using the novelcompositions it is possible to produce relief images for printedcircuits or printing plates directly by irradiation of the mixtures, forexample by means of a computer-controlled laser beam of appropriatewavelength or employing a photomask and an appropriate light source.Alternatively, the compositions may be printed using piezo ink jettechnology directly onto printing plates or circuit boards, and cured byoverall or selective irradiation.

The invention further provides the use of a complex of a Lewis acid anda Lewis base (wherein the Lewis acid is other than a fluorine-containingboron compound) as a stabiliser for a composition containing at leastone actinic radiation curable, cationic ring opening compound and atleast one cationic photoinitiator for said cationically polymerisablecompound. The invention further provides a process for the stabilizationof a composition containing

-   (A) at least one actinic radiation curable, cationically    polymerisable compound; and-   (B) at least one cationic photoinitiator for component A); which    comprises admixing with said components (A) and (B), a complex of a    Lewis acid and a Lewis base (the Lewis acid being other than a    fluorine-containing boron compound) in an amount such that the    composition is stabilised in relation to the corresponding    composition not containing said complex.

The following Examples illustrate the invention.

In Examples 1 to 23, the use of boron trichloride/dimethyloctylaminecomplex (DY9577, from Vantico Ltd) as a viscosity stabiliser in cationicformulations is exemplified, and compared to the resin withoutstabiliser. Examples 24 to 41 illustrate the use of furtherboron-containing complexes, while Examples 42 to 44 illustrate the useof iron-containing complexes. Examples 54 to 59 are comparativeexamples.

EXAMPLE 1

180 g of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate(Uvacure 1500, manufactured by Dow Chemicals) was mixed with 20 g ofmixed triarylsulfonium hexafluoroantimonate salts in 50% by weightpropylene carbonate (Cyracure 6976, supplied by Dow Chemicals). Thisliquid composition 1 was then used in examples 2-5, 36-41 and 45-53.

EXAMPLE 2

To 20 g of liquid composition 1 was added 4.1 mg of DY9577 (MW=275.15g/mol) in a brown Nalgene bottle. The mixture was stirred on a rollermixer for 5 hours at room temperature. In Example 2, the liquidcomposition 1 contains 204 parts per million of DY9577 (0.0204 wt %;0.74 mmol per kilogram of resin).

EXAMPLES 3 AND 4

Mixtures characterised by the compositions listed in table 1 wereprepared as in example 2. The quantitative data in table 1 are wt %. Forcomparison purposes, the amount of stabiliser is also given in mmol perkilogram of resin (mmol/kg).

TABLE 1 Example No. DY9577 wt % (mmol/kg) 3 0.041 (1.49) 4 0.055 (2.00)

Liquid composition 1 and examples 2 to 4 (contained in sealed, brownNalgene bottles) were placed in an oven at 65° C. to perform acceleratedageing. The viscosity was measured every 2-3 days (Brookfield DVII2, HB,cone and plate, Spindle S40, 10 rpm). Viscosities at 25° C. (mPa·s) arereported in table 2. Liquid composition 1 was chosen as a generalcationic photocurable composition to demonstrate the stabilising effectof DY9577. Accelerated ageing at 65° C. reveals how stable/unstable aliquid composition can be upon storage. When applied to kineticallycontrolled reaction rates, the Arrhenius equation predicts that a 10° C.increase in temperature will double the reaction rate. A 2-weekstability test at 65° C. is equivalent to over 7 months storage at 25°C.

TABLE 2 day 0 3 9 Liquid composition 1 238 311 24300 (comparison)Example 2 238 320 1000 Example 3 238 299 880 Example 4 238 294 820As shown here, when used in small amounts, far from initiating thepolymerisation of the epoxies, DY9577 slows down significantly theageing process of the cycloaliphatic epoxy in the presence of a cationicphotoinitiator at 65° C. This is a most unusual result, as DY9577 is alatent thermal catalyst for epoxies.

EXAMPLE 5

The liquid composition 2 described in Table 3 was the base forexperiments performed to assess the performance of DY9577 as a viscositystabiliser in a typical photocurable composition used instereolithography.

TABLE 3 Class of compound Commercial name Manufacturer Wt %Cycloaliphatic Uvacure 1500 Dow Chemicals 48.5 epoxide Glycidyl ethersHeloxy 48 Resolution 11.0 Heloxy 84 Resolution 6.1 Acrylates SR399Sartomer 6.1 Ebecryl 3700 UCB chemicals 6.3 polyol Terathane 1000 DuPont 15.0 Free-radical Irgacure 184 Ciba SC 2.0 Photoinitiator CationicCyracure 6976 Dow Chemicals 5.0 Photoinitiator

The components were stirred at 60° C. until a clear homogeneous mixtureformed.

EXAMPLE 6

To 31.1 g of liquid composition 2 was added 6.3 mg of DY9577 (MW=275.15g/mol) in a brown nalgene bottle. The mixture was stirred on a rollermixer for 5 hours at room temperature. In Example 6, the liquidcomposition 2 contains 203 parties per million of DY9577 (0.0203 wt %;0.74 mmol per kilogram of resin).

EXAMPLES 7-17

Mixtures characterised by the compositions listed in table 2 wereprepared as in example 6. The quantitative data in table 4 are weightpercent (wt %). For comparison purposes, the amount of stabiliser isalso given in mmol per kilogram of resin (mmol/kg).

TABLE 4 Example No. DY9577 wt % (mmol/kg)  7 0.0407 (1.48)  8 0.0548(1.99)  9 0.0680 (2.47) 10 0.0800 (2.91) 11 0.0961 (3.49) 12 0.108(3.94) 13 0.152 (5.52) 14 0.200 (7.26) 15 0.300 (10.89) 16 0.499 (18.14)(comparison) 17 1.000 (36.31) (comparison)

The photospeed of the compositions listed in table 4 were determinedusing methods well known in the art, using a SLA apparatus (SLA 70003D-Systems). Depth of Penetration (Dp, in mils) and Critical Exposure(Ec, in mj/cm²) are given in table 5. Also listed are E4 and E11, theenergies respectively needed to cure layers of 4 and 11 mils ofthickness.

TABLE 5 Composition Dp (mils) EC (mj/cm²) E4 (mj/cm²) E11 (mj/cm²)Liquid 5.09 7.43 16.31 64.591 composition 2 (comparison) Example 6 4.876.95 15.796 66.425 Example 7 5.13 7.77 16.954 66.387 Example 8 5.19 7.8216.891 65.043 Example 9 4.88 6.73 15.293 64.251 Example 10 5.11 7.5616.531 65.070 Example 11 5.02 7.43 16.488 66.561 Example 12 5.05 7.6516.882 67.534 Example 13 4.94 7.08 15.921 65.731 Example 14 4.97 7.2716.242 66.372 Example 15 4.94 7.10 15.961 65.889

The data gathered in Table 5 show that the boron-amine complex does notsignificantly affect the photospeed of the stereolithography resin. Thisis a crucial result. Due to their basic character viscosity stabilisersare expected to reduce the photospeed of UV-curable resins. Finding aviscosity stabiliser that will capture the acid species created uponageing without affecting the cure properties of the resin is a realbreakthrough.

EXAMPLE 18

Thermal ageing at 65° C. was performed on the compositions of examples6-17. Samples were placed in sealed brown Nalgene bottles at 65° C. Theviscosities measured every 2-3 days are reported in table 6.

The accelerated ageing at 65° C. shows very clearly that small amountsof DY9577 are very effective at slowing down the ageing process ofliquid composition 2. Without any stabiliser, the resin gels after 11days at 65° C., whereas small amounts of DY9577 increases its storagestability, slowing down the ageing process and deferring the gellingtime. However, increasing the amount of DY9577 represents a danger, asshown in comparative examples 16 and 17, containing 0.5 and 1.0 wt % ofthe stabiliser. At these levels, DY9577 does not act as a stabiliser anylonger, but acts as a thermal catalyst and induces gelling within a day.

TABLE 6 Day 0 1 3 4 5 6 7 8 10 11 13 14 17 24 Liq. comp. 2 421 437 5912420 8850 gel (comparison) Ex. 6 450 528 567 602 Ex. 7 429 450 450 497Ex. 8 426 450 453 484 Ex. 9 426 450 458 487 Ex. 10 450 468 910 Ex. 11450 466 520 528 Ex. 12 450 481 546 529 Ex. 13 460 466 534 518 570 Ex. 14460 476 544 544 600 Ex. 15 460 505 583 600 680 Ex. 16 460 Partial(comparison) gel Ex. 17 460 partial (comparison) gel

EXAMPLE 19-21

Green flexural modulus (GFM) of liquid composition 2, example 7 andexample 9 were measured. 150 g of resin were placed in a small tub and 3flexural bars (2.66×6.23×40 mm) were built with a SLA 7000 (3D-Systems).The flexural modulus at 1 mm deflection is measured 10 min and 1 hourafter the end of the build. The 3rd bar is kept for 48 hours at 25° C.,50% relative humidity, and UV-cured for 90 min in a PCA oven. The greenflexural modulus in MPa after 10 min, 1 hour, and after UV-curing aregiven in table 7.

TABLE 7 10 min-GFM 1 h-GFM UV-cured Liquid composition 2 17 85 1430Example 7 19 84 1470 Example 9 14 78 1460

This example demonstrates that DY9577 used in an appropriate amount doesnot affect the green strength of a stereolithography part. Greenstrength is a major property in stereolithography: the parts built bythis process must be strong enough to stand without collapsing undertheir own weight and to be removed from the metallic platform on whichthey have been built without damage. DY9577 does not affect thephotospeed, the green strength or the final flexural modulus of thecured material, as compared to the non-modified resin, and does increasethe storage stability of the liquid resin.

EXAMPLE 22

The liquid composition 3 described in Table 8 is used in a test designedto mimic the formation of free acid in a vat in a SLA apparatus. Theviscosity of the liquid composition 3 is 380 mPa·s at 25° C., and theepoxy value is 5.86 mol/kg.

TABLE 8 Class of compound Commercial name Manufacturer wt %Cycloaliphatic Uvacure 1500 Dow Chemicals 50.2 epoxide Glycidyl ethersHeloxy 48 Resolution 30.0 Acrylates SR399 Sartomer 6.2 Ebecryl 3700 UCBchemicals 6.3 Free-radical Irgacure 184 Ciba SC 2.5 PhotoinitiatorCationic Cyracure 6976 Dow Chemicals 5.0 Photoinitiator

437 g of liquid composition 3 are placed in a small plastic tub. A3-dimension part made of fine supports, referred to as the “sponge part”is built with a SLA 7000 (3D-Systems). Ideally, the part occupies thelargest possible volume of the small tub of resin. When building thefine part, the laser will also slightly irradiate the surrounding liquidresin thus producing unwanted acid species that can start polymerisingthe epoxy monomers. The fine structure of the test part is designed toamplify this effect resulting in increased viscosity. In total, threesponge parts are built in the same resin, at 24 hour intervals, and theviscosity of the resin is measured just before the following test (23hours after the end of the previous build), after draining the previoustest part (Table 9). Epoxy values also confirm that the increasedviscosity is due to the uncontrolled polymerisation of the epoxidemonomers (decreasing epoxy value after several sponge tests).

TABLE 9 Viscosity at Epoxy value 25° C. (mPa · s) (mol/kg) Before test380 5.86 23 h after 1 sponge 460 (+21%) 5.78 23 h after 2 sponges 680(+79%) 5.65 23 h after 3 sponges 1375 (+262%) 5.58

EXAMPLE 23

To 471.7 g of liquid composition 3 were added 373 mg of DY9577 (0.079 wt%; 2.87 mmol/kg). The mixture was stirred for 1 hour before 437 g wereplaced in a tub and the experiment described in example 25 was repeated.The results are reported in Table 10.

TABLE 10 Viscosity at 25° C. Epoxy value (mPa · s) (mol/kg) Before test380 5.86 23 h after 1 sponge 400-415 (+5-9%) 23 h after 2 sponges500-525 (+31-38%) 23 h after 3 sponges 580 (+53%) 5.75Examples 22 and 23 show the remarkable effect of DY9577 as a viscositystabiliser. The increase in viscosity for the resin stabilised with0.079 wt % of DY9577 is much less dramatic than the original resin. Thedecrease in the epoxy value further demonstrates that the viscosity riseis due to the gelling of the epoxides.

EXAMPLES 24-35

The liquid composition 2 described in example 5 was used to assess theperformance of borane trimethylamine (BH₃/NMe₃) complex. Mixturescharacterised by the compositions listed in table 11 were prepared as inexample 2. The quantitative data in table 11 are wt %. For comparisonpurposes, the amount of stabiliser is also given in mmol per kilogram ofresin (mmol/kg).

TABLE 11 Example No. BH₃/NMe₃ wt % (mmol/kg) 24 0.0109 (1.49) 25 0.0183(2.50) 26 0.0286 (3.92) 27 0.0309 (4.24) 28 0.0474 (6.50) 29  0.0732(10.03)Thermal ageing at 65° C. was performed on the compositions of examples24-29 as described in example 18. The viscosities are reported in table12. These examples show that BH₃/NMe₃ is as good as DY9577 and preventsthe thermal cure of the epoxide.

TABLE 12 Day 0 2 6 9 15 Liq. Comp. 2 473 500 1000 1800 gel (comparison)Ex. 24 456 445 458 524 600 Ex. 25 470 463 470 491 475 Ex. 26 458 463 466511 500 Ex. 27 458 452 453 510 500 Ex. 28 472 420 479 490 500 Ex. 35 472458 490 520 550

EXAMPLES 36-41

The liquid composition 1 described in example 1 was used to assess theperformance of 2 other commercial borane/amine complexes andborane/phosphine complexes. Borane tributylphosphine (BH₃/PBu₃) andborane ammoniac (BH₃/NH₃) complexes were bought from Aldrich. Mixturescharacterised by the compositions listed in table 13 were prepared as inexample 2. The quantitative data in table 13 are wt %. For comparison,the amount of stabiliser is also given in mmol per kilogram of resin(mmol/kg).

TABLE 13 BH₃/PBu₃ wt % BH₃/NH₃ wt % Example No. (mmol/kg) (mmol/kg) 360.0320 (1.48) 37 0.0870 (4.01) 38  0.216 (10.00) 39 0.0046 (1.48) 400.0123 (3.98) 41 0.0309 (10.0)Thermal ageing at 65° C. has been performed on the compositions ofexamples 36-41 as described in example 18. The viscosities are reportedin table 14.

TABLE 14 Day 0 3 6 Liq. Comp. 1 (comparison) 203 1180 20000 Ex. 36 205216 301 Ex. 37 205 213 204 Ex. 38 205 211 211 Ex. 39 205 495 1055 Ex. 40205 205 293 Ex. 41 205 249 298

EXAMPLES 42-44 Synthesis of iron trichloride/amine Complexes EXAMPLE 42Iron trichloride dimethyloctylamine Complex (FeCl₃/N(CH₃)₂ (C₈H₁₇)Complex)

Solution 1: 0.382 g of FeCl₃ (2.355 mmol) is weighed in a small jar and9.918 g of CHCl₃ are added (3.7 wt % of FeCl₃ in solvent).

Solution 2: 0.373 g of N(CH₃)₂ (C₈H₁₇) (2.37 mmol) are weighed in a jarand dissolved in 10.09 g of CHCl₃ (3.6 wt % in solvent).

Solution 2 is added dropwise at room temperature to solution 1 whilestirring. The formation of the complex results in solubilisation ofFeCl₃ and the mixture becomes red-brown. Stirring is maintained during 1hour before the solvent is removed under reduced pressure. The materialis dried under reduced pressure at room temperature until the weightremains constant. FeCl₃/N(CH₃)₂(C₈H₁₇) is a red-brown viscous liquid,with an unpleasant odour. Final weight: 0.72 g (yield=92%)

EXAMPLE 43 Iron trichloride pyridine Complex (FeCl₃/pyridine Complex)

Solution 1: 0.541 g of FeCl₃ (3.33 mmol) in CHCl₃ (2.8 wt % solution)

Solution 2: 0.265 g of pyridine (3.35 mmol) in CHCl₃ (5.8 wt % solution)

Solution 2 is added to solution 1 in the same manner as in example 42.FeCl₃/pyridine complex is a yellow powder, filtered off on a No. 4filter paper, and rinsed with CHCl₃ until CHCl₃ remains uncolored.FeCl₃/pyridine complex has a melting point of 113-116° C. Final weight:0.515 g (yield=64%)

EXAMPLE 44 Iron trichloride triethylamine Complex (FeCl₃/NEt₃ Complex)

Solution 1: 0.492 g of FeCl₃ (3.03 mmol) in CHCl₃ (3 wt % solution)

Solution 2: 0.308 g of NEt₃ (3.04 mmol) in CHCl₃ (5.2 wt % solution)

Solution 2 is added to solution 1 in the same manner as in example 42.The FeCl₃/NEt₃ complex is a dark red oil floating at the surface ofCHCl₃. The solvent is evaporated as in example 42. FeCl₃/NEt₃ complex isa dark red viscous liquid with an unpleasant odour. Final weight: 0.72 g(yield=90%).

These three new complexes are used in the following examples todemonstrate that FeCl₃/amines are suitable complexes for the invention.

EXAMPLES 45-53

The liquid composition 1 described in example 1 was used to assess theperformance of new iron trichloride/amine complexes as stabilisers incationically curable compositions. Mixtures characterised by thecompositions listed in table 15 were prepared as in example 2. Thequantitative data in table 15 are wt %. For comparison purposes, theamount of stabiliser is also given in mmol per kilogram of resin(mmol/kg).

TABLE 15 FeCl₃/N(CH₃)₂(C₈H₁₇) FeCl₃/pyridine FeCl₃/NEt₃ Example No. wt %(mmol/kg) wt % (mmol/kg) wt % mmol/kg) 45 0.047 (1.46) 46 0.128 (4.00)47  0.320 (10.00) 48 0.040 (1.50) 49 0.106 (4.02) 50 0.263 (9.99) 510.036 (1.48) 52 0.095 (3.93) 53 0.241 (9.98)Thermal ageing at 65° C. has been performed on the compositions ofexamples 45-53 as described in example 18. The viscosities are reportedin table 16. Examples 45 to 53 show that iron trichloride/aminecomplexes are effective viscosity stabilisers for cationically curableresins.

TABLE 16 Day 0 3 6 Liq. Comp. 1 (comparison) 203 1180 20000 Ex. 45 207217 247 Ex. 46 205 246 242 Ex. 47 203 249 277 Ex. 48 205 226 621 Ex. 49205 246 252 Ex. 50 206 240 245 Ex. 51 205 231 486 Ex. 52 205 247 249 Ex.53 206 310 322

EXAMPLES 54 TO 59 (COMPARISON)

The method of Examples 24 to 35 was repeated using borontrifluoride-ethylamine complex. The results are shown in Table 17.

TABLE 17 BF₃/NH₂Et Viscosity Viscosity Example No. wt % (mmol/kg) at 0days at 2 days Liq. Comp. 2 0 473 500 (comparison) 54 0.0167 (1.48) 480877 55 0.0283 (2.51) 466 1130 56 0.0393 (3.48) 472 1520 57 0.0507 (4.49)485 58 0.0793 (7.03) 458 4450 59  0.1187 (10.51) 472 1500The results plainly show that compositions containing boron trifluoridecomplexes are relatively unstable in comparison to compositionsaccording to the invention.

1. An actinic radiation curable composition comprising: (A) 40-80 weight% of at least one liquid epoxy resin having an epoxy functionality of 2or greater; (B) 0.1-10 weight % of at least one cationic photoinitiator;(C) 5-40 weight % of at least one liquid diacrylate; (D) 0-15 weight %of at least one liquid poly(meth) acrylate having a (meth)acrylatefunctionality of greater than 2; (E) 0.1-15 weight % of at least oneradical photoiniator; (F) 5-40 weight % of at least one OH-terminatedpolyether, OH-terminated polyester or OH-terminated polyurethane; and(G) 0.001-0.3 weight % of at least one stabilizer selected from thegroup consisting of borane ammoniac complex, borane triethylaminecomplex, borane tributylphosphine complex, borane trimethylaminecomplex, borane triphenylphosphine complex, borane tributylaminecomplex, borane N,N-diethylamine complex, borane N,N-diisopropylethylamine complex, borane dimethylamine complex, boraneN-ethyl-N-isopropyl aniline complex, borane 4-methyl-morpholine complex,borane 4-ethylmorpholine complex, bis-(triethylborane) 1,6-diaminohexanecomplex, trichloroborane N,N-dimethyloctylamine complex, trichloroboraneN,N-dimethyloctylamine complex, trichloroborane triethylamine complex,trichloroborane pyridine complex, trichloroborane benzylamine complex,irontrichloride triethylamine complex, irontrichloride pyridine complex,and irontrichloride N,N-dimethyloctylamine.
 2. The actinic radiationcurable composition of claim 1 wherein the stabilizer is selected fromthe group consisting of borane trimethylamine complex, boranetributylphosphine complex, borane ammoniac complex, bis-(triethylborane)1,6-diaminohexane complex, trichloroborane triethylamine complex,trichloroborane pyridine complex, trichloroborane benzylamine complex,irontrichloride triethylamine complex, irontrichloride pyridine complex,and irontrichloride N,N-dimethyloctylamine.
 3. The actinic radiationcurable composition of claim 1 wherein the epoxy resin is acycloaliphatic diepoxide.
 4. The actinic radiation curable compositionof claim 3 wherein the cycloaliphatic diepoxide has a monomer purity of90% or higher.
 5. The actinic radiation curable composition of claim 1wherein two or more epoxy resins are present.
 6. The actinic radiationcurable composition of claim 5 wherein the two or more epoxy resins arecycloaliphatic diepoxides independently selected from the groupconsisting of bis(4-hydroxycyclohexyl)methane diglycidyl ether;2,2-bis(4-hydroxycyclohexyl) propane diglycidyl ether;3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate;3,4-epoxy-6-methyl-cyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate;di-(3,4-epoxycyclohexylmethyl) hexanedioate;di-(3,4-epoxy-6-methyl-cyclohexylmethyl) hexanediotate;ethylenebis(3,4-epoxycyclohexanecarboxylate), ethanedioldi-(3,4-epoxycyclohexylmethyl) ether and2-(3,4-epoxycyelohexyl-5,5,3-dioxane).
 7. The actinic radiation curablecomposition of claim 1 wherein the cationic photoiniator is an oniumsalt with an anion of weak nucleophilicity.
 8. The actinic radiationcurable composition of claim 7 wherein the onium salt comprises an oniumsalt of formula (III), (IV) or (V):

wherein each of R₁, R₂, R₃, R₄, R₅, R₆ and R₇ are independently selectedfrom a C₆-C₁₈ aryl which may be optionally substituted by appropriateradicals; A is CF₃SO⁻ ₃ or an anion having the formula [LQ_(m)]⁻ where Lis selected from the group consisting of boron, phosphorus, arsenic andantimony; Q is a halogen or hydroxyl group; and m is an integercorresponding to the valency of L enlarged by
 1. 9. The actinicradiation curable composition of claim 8 wherein the onium salt is acompound having formula (V) and R₅, R₆ and R₇ are independently selectedfrom the group of phenyl and biphenyl.
 10. The actinic radiation curablecomposition of claim 1 wherein the OH-terminated polyether has amolecular weight ranging between 250 to
 4000. 11. A method for producinga cured product comprising treating an actinic radiation curablecomposition according to claim 1 with actinic radiation.
 12. A methodfor producing a stabilized actinic radiation curable compositioncomprising mixing: (A) 40-80 weight % of at least one liquid epoxy resinhaving an epoxy functionality of 2 or greater; (B) 0.1-10 weight % of atleast one cationic photoinitiator; (C) 5-40 weight % of at least oneliquid diacrylate; (D) 0-15 weight % of at least one liquidpoly(meth)acrylate having a (meth)acrylate functionality of greater than2; (E) 0.1-15 weight % of at least one radical photoiniator; (F) 5-40weight % of at least one OH-terminated polyether, OH-terminatedpolyester or OH-terminated polyurethane; with (G) 0.001-0.3 weight % ofat least one stabilizer selected from the group consisting of boraneammoniac complex, borane triethylamine complex, borane tributylphosphinecomplex, borane trimethylamine complex, borane triphenylphosphinecomplex, borane tributylamine complex, borane N,N-diethylamine complex,borane N,N-diisopropyl ethylamine complex, borane dimethylamine complex,borane N-ethyl-N-isopropyl aniline complex, borane 4-methyl-morpholinecomplex, borane 4-ethylmorpholine complex,bis-(triethylborane)1,6-diaminohexane complex, trichloroboraneN,N-dimethyloctylamine complex, trichloroborane N,N-dimethyloctylaminecomplex, trichloroborane triethylamine complex, trichloroborane pyridinecomplex, trichloroborane benzylamine complex, irontrichloridetriethylamine complex, irontrichloride pyridine complex, andirontrichloride N,N-dimethyloctylamine.